The last time I hatched 40 eggs and 1 rare egg (Era of dragons) it was the worst ever got only two five star monsters out of which one I already had and other one isn’t that good and I would never used in a battle. Even the rare egg monster was just a 5 star, don’t remember who but wasn’t a great hatch.
The sad part is this happened even though I was told to hatch only in festivals but because I had a lot of training points left and needed more monsters to complete missions so got impatient and hatched it.
Would like the members here to guide me the next time a festival comes, we could analyse the monsters and update if it’s the best time to hatch then 
I have 40 gems and 2 rare eggs so hopefully I am hoping for 3 six stars this time.